Voltage regulator and method



June 19, 1962 l. WUNDERMAN 3,040,241

VOLTAGE REGULATOR AND METHOD Filed April 2, 1958 5% WWW l9 I/ZPP/MERES/STOR /4 l2; .1 /7

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ATTORNEYS United States Patent Ofiiice 3,040,241 Patented June 19, 1962 3,043,241 VOLTAGE REGULATOR AND METHOD Irwin Wonder-man, Mountain View, Calif., assignor to Hewlett-Packard Company, Palo Alto, Caiif., a corperation of California Filed Apr. 2, 1958, Ser. No. 725,877 3 Claims. (Cl. 323-66) This invention relates generally to a voltage regulator and method and more particularly to a voltage regulator and method which includes photoresistive control elements.

As is well known, a voltage regulator is a device which serves to maintain the output voltage at constant rated value with variations in the input voltage. The regulator reacts automatically within its rated limits to any variation in the input voltage. Thus, if the input voltage rises or falls, the voltage regulator automatically compensates for the change and maintains the output voltage at a substanially constant value.

Voltage regulators have been constructed in various forms and in a number of circuit arrangements. In general, voltage regulators have been employed to regulate D.-C. Alternating current voltages have been regulated by means of special types of transformers and the like.

It is a general object of the present invention to provide a novel voltage regulator and method which makes use of photoresistors for regulating the output voltage.

It is another object of the present invention to provide a voltage regulator which makes use of photoresistors and variable light sources for regulating the output voltage.

It is another object of the present invention to provide a voltage regulator and method which may be employed for controlling either AC. or D.-C. voltages as desired.

The invention possesses other objects and features of advantage, some of which with the foregoing will be set forth in the following description of the invention. It is to be understood, of course, that the invention is not to be limited to the disclosure of a particular species of the invention, as other embodiments thereof may be adopted within the scope of the claims.

Referring to the drawing:

FIGURE 1 is a circuit diagram of a shunt voltage regulator;

FIGURE 2 is a plan view of a photoresistive network including interdigital lines;

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 2;

FIGURE 4 is a shunt regulator which includes an additional light source and photoresistors; which combination provides active gain; and

FIGURE 5 is a series regulator which has a reference scheme similar to that of FIGURE 4.

Referring to FIGURE 1, the regulator comprises a pair of lines 11 and 12 having input terminals 13 and 14 and output terminals 16 and 17. A resistor 18 is connected in series with the line 11. A suitable glow tube regulator 19, for example, a neon bulb is connected in shunt across the lines 11 and 12. A photoresistor 21 is also connected in shunt across the lines and disposed whereby it is illuminated by light from the neon bulb 19, as indicated by the arrow 22.

The photoresistor 21 may be of the interdigital type illustrated in FIGURES 2 and 3. The photoresistor comprises a pair of interdigital conductive structures 23 and 24 which are carried by an insulating member 26. A layer of photoconductive material 27 is disposed over the interdigital conductors 23 and 24 and serves to interconnect them. When light impinges on the photoconductive layer 27, the resistance between elements decreases. When the amount of illumination decreases, the resistance increases. Thus, the resistor is sensitive to the intensity of illumination.

The layer 27 may be formed by dispersing photoconductive powders in a suitable binder which is then applied to the surface of the structure in the form of a layer. The binder is air dried leaving a layer with the particles of photoconductive material adjacent one another to form a continuous conductive layer which is responsive to illumination. Alternatively, the layer may be sintered to form a relatively continuous layer 27 of photoconductive material. Other means well known in the art may be employed for forming the photoconductive resistor.

Referring again to FIGURE 1, the regulator operates as follows: As the voltage between the terminals 16 and 17 increases the intensity of illumination from the neon bulb 19 increases to thereby increase the light impinging on the photoresistor 21. With an increase of light, the resistance of the photoresistor decreases. Therefore, the voltage which appears across the element 21 decreases since its resistance in comparison to the element 18 decreases. Thus, the proportion of the voltage across the resistor 21 is decreased to compensate for the increase of voltage. The voltage at the terminals 16, 17 remains constant. The voltage variations at the terminals 16 and 17 may be due to changes in load or changes in the voltage applied to the terminals 13 and 14.

Referring now to FIGURE 4, a shunt regulator of the type illustrated and described with reference to FIGURE 1 is shown. The regulator of FIGURE 4 includes an additional light source and photoresistor for increasing the active gain of the regulator.

The regulator includes the lines 31 and 32 having input terminals 33 and 34 and output terminals 36 and 37. A resistor 33 is connected in series in the line 31. A glow tube 39 is connected in shunt across the lines 31 and 32 as indicated. A photoresistive element 41 is connected in series with an incandescent lamp 42 across the lines. The photoresistor 41 is disposed whereby it is illuminated by light from the neon bulb 39 as indicated by the arrow 43. A second photoresistive element 44 is connected in shunt with the lines 31 and 32 and is disposed whereby it is illuminated by the incandescent lamp 42 as indicated by the arrow 46. An incandescent lamp may be used when slow A.C. regulation is desired. The lamp serves to average out the sampling pulses.

Operation of the circuit is as follows: When the voltage across the terminals 36 and 37 increases, the light output of the neon bulb 39 increases; when the input voltage exceeds the regulating voltage of the neon glow tube 39, the light output increases. The increased light reduces the average value of the photoresistor 41 and the intensity of the incandescent lamp 42 then increases. The illumination from the lamp 42 strikes the photoconductor 44 which is the major current consumer. The increase in current drawn through the resistor 38 brings the voltage at the point 36 back towards the point where the current through the neons remains fixed. By suitably choosing the value of the resistors 41 and 44, the output wave form distortion may be minimized. This may be achieved by having most of the regulating current travelling through the resistor 44, or by permitting resistor 41 to have a long time constant.

Referring to FIG. 5, series regulation can be achieved by simply placing a series photoresistor 51 in the line 52. The circuit then includes a glow regulator tube 53 in shunt with the lines 52 and 54. An incandescent lamp 56 connected in series with a photoresistor 57 also connected in shunt between the lines 52 and 53. The photoresistor 57 is disposed whereby it is illuminated by the light from the glow tube 53 as indicated by the arrow 58. A photoresistor 59 is connected in shunt with an incandescent lamp 61. The shunt combination of resistor 59 and lamp 61 is connected in series with a fixed resistor 62 across the lines 52, 54. The photoresistor 59 is disposed to be illuminated by light from the incandescent lamp 56 as indicated by the arrow 63 and the incandescent lamp 61 is disposed whereby it illuminates the series photoresistor 51 as indicated by the arrow 64.

Operation of the circuit is as follows: When the voltage between the lines 52, 54 increases, the glow tube 53 light output increases. The resistance of photoresistor 57 decreases, increasing the current through the incandescent lamp 56 and increasing its light output. This decreases the resistance 59 shunting the lamp 61 thereby decreasing the light output from the lamp 61. The effect of the gain of the previous two stages in decreasing the light output of the lamp 61 is greater than the increased voltage at the input causing lamp 61 to glow brighter. Hence the resistance of photoresistor 51 increases and the voltage at the output is brought back toward the original value.

Apparatus was constructed in accordance with FIG- URE 4 in which the resistor 38 had a value of 1800 ohms, the glow tube 39 was known by manufacturers spec. as NE16, the incandescent lamp 42 was of the type known by manufacturers spec. as 3W 120V, and the photoresistors 41 and 44 had a dark resistance of 5 megohms. The circuit was operated and the input voltage was varied between 95 and 140 volts. The output voltage was maintained constant within two volts for the indicated variation. Thus, it is seen that a relatively etficient voltage regulator is provided.

Thus, it is seen that photoresistors are employed in a novel manner to form a voltage regulator which is suitable for regulating either A.-C. or DC. voltages as desired. The regulator is simple and inexpensive to construct, and reliable in operation.

I claim:

1. A voltage regulator comprising first and second lines having input and output terminals, a resistor connected in series with one of said lines, a glow tube regulator connected in shunt with the output terminals, a photoresistive element and an incandescent bulb connected in series across said lines, said photoresistive clement adapted to be illuminated by the glow tube, and a photoresistive element connected in shunt with the output terminals and adapted to be illuminated by the incandescent lamp.

2. Apparatus as in claim 1 wherein said last photoresistive element has a resistance substantially less than the resistance of the first element.

3. A voltage regulator comprising first and second lines having input and output terminals, a first photoresistive element connected in series with one of said lines, a glow tube regulator connected across said output terminals, a second photoresistive element and a first incandescent bulb connected in series across said lines, said second photoresistive element adapted to be illuminated by said glow tube, a second incandescent bulb and a resistor connected in series across said lines, said first photoresistive element adapted to be illuminated by said second incandescent bulb, and a third photoresistive element connected in shunt with said second incandescent bulb, said third photoresistive element adapted to be illuminated by said first incandescent bulb.

References Cited in the file of this patent UNITED STATES PATENTS 1,107,438 Moskowitz Aug. 18, 1914 2,181,579 Custis Nov. '28, 1939 2,356,195 Balsley Aug. 22, 1944 2,369,675 Houghton Feb. 20, 1945 2,736,848 Rose Feb. 28, 1956 FOREIGN PATENTS 540,468 Italy Mar. 5, 1956 

